Historically, simple backlight devices included only three main components: light sources or lamps, a back reflector, and a front diffuser. Such systems are still in use for general purpose advertising signs and for indoor lighting applications.
Over recent years, refinements have been made to this basic backlight design, fueled by demands in the high-growth consumer electronics industry for products that incorporate liquid crystal displays (LC displays, or LCDs), such as computer monitors, televisions, mobile phones, digital cameras, pocket-sized digital music players, and other hand-held devices. An LCD is built around an LC panel, and, because LC panels do not create light themselves, an LCD requires a source of illumination—typically either reflected ambient light, or more commonly, light from a backlight that passes through the LC panel to reach the viewer.
Refinements in backlight technology are directed toward goals such as increasing brightness or reducing power consumption, increasing uniformity, and reducing thickness. Some of these refinements can be achieved through the use of light management films such as light redirecting films (e.g., gain diffusers, turning films, prismatic brightness enhancement films, etc.) and reflective polarizing films that enable more effective and efficient use of the light emitted by the light sources in a backlight. In addition to the desire for improved technical performance, backlight makers are also motivated to provide lower cost products.